Dolph:
I’m curious if UK leaves EU and EU somehow remain stable and functioning, how do you imagine you life - economy, work, travel in the mainland Europe? What will happen with trade and manufacturing etc.? Will UK remain as it is or some countries(Scotland) will want out and join EU by themselves?
What will happen with the Brits living, working and owning property in EU countries? Are they going to be deported for not meeting the EU visa criteria 
What needs to change on exit?
Let’s look at Calais as an example:
Trade routes themselves would not cease on Britain leaving the EU. The EU would be cutting off their noses to spite their faces if they embarked on some kind of blockade to British trade (an act of war!) or attempted to surcharge British Truckers passing through Calais (Ermmm… There’s few enough left as it is!)
Then there’s the issue of what is to be done with EU truckers passing through Calas to Britain, where they plough up our roads, don’t pay our road taxes, and even fuel up their supersized tanks in France where Derv is cheaper, tramp around Britain, and return without having filled up in Britain at all…
My suggest is therefore that the only punitive action that would actually HURT us from across the sea - is the kind of action that is an act of war.
IF the trade routes get broken up, then it would be easy to circumvent France outright - if it came to that.
As has been pointed out already - Zeebrugge, Oostende, Hoek van Holland, Bilbao, Rotterdam, etc. would welcome additional trade traffic to and from Britain with open arms I’m sure…
What’s more likely - is that Britain pulling out of the EU would be the final kick in the pants for France to do what needs to be done, elect their FN government, and we can sit in our armchairs watching a new French security force mow down charging immigrants armed with bricks & iron bars, etc. Once we’re no longer using Calais, the French will embark upon the hard answer being the solution to what should have always been 100% of THEIR problem from the very beginning.
Get tough, or get out.
The UK has the option of “Getting Out”. Let’s do that. Britain has the rest of the world to trade with. Calais only has England. They need us - we don’t need them. 
)
Your words remind me of when people from the Balkans argue about history, we are mega pathetic at it. I’m glad that people are more and more open minded about our past and look at the future.